Electrodynamic device



April 30, 1963 D. KLEls ETAL 3,088,001

mcmonmurc DEVICE 3 .ZZT

, INVENTORS DERK KLEIS AGENT United Smtes PatentOice 3,0S8,tl01 ELECTRODYNAMIC DEVICE Derk Kleis, Gerrit Schenkel, and Adrianus Bierens, Eindhoven, Netherlands, assignors to North American Philips Company, Inc., New York, NX., a corporation p This invention relates to electrodynamic devices or i1 electrical transducers comprising a diaphragm and a coil lglued thereto with one end surface, more particularly microphones or loudspeakers. Direct adhering of the coil to the diaphragm is necessary if the coil former on which the coil is wound is very thin-Walled or wholly absent,'

as is particularly desirable in the case of microphones.

In order to ensure satisfactory adhesion of the end surface of the coil to the diaphragm, it is naturally of paramount importance for the end surface to be formed as regularly as possible, that is to say, to be as flat as possible, in order to make it adhere to the locally at daphragm through as large a surface area as possible.

A second condition is that the two ends of the winding wire shall leave the coil in the relevant end surface in approximately tangential directions and preferably at diametrically opposite points so as to enable these wire ends to be likewise glued to the diaphragm.

An object of the invention is to provide a device in which said requirements are fulfilled as well as possible.

The device is characterized in that the largest portion of each turn and of the turn located above and/or below it is located in one plane at right angles to the axis of the coil, and that the first and the last turn respectively of the outer layer of the coil embraces the other layers through an angle a of less than 360 and at the most the complementary angle 360-a respectively, While the winding wire at the free end of the iirst turn of the coil located directly under the last turn runs back bilarly with the first turn in line with the said last turn through at the most the angle a.

In order that the invention may be readily carried into effect, it will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawing, in which FIGS. la and lb illustrate the manufacture of a coil according to the invention;

FIGS. 2 and 3 are an axial cross-section and an axial View respectively, of one embodiment of a coil according to the invention, and

FIG. 4 shows an axial cross-section of a variant of the coil according to the invention.

FIGS. la and lb each show part of a coil according to the invention having two winding layers, which coil is still on the winding mandrel. The two layers are shown separately in FIGS. la and lb for the sake of clarity, but the layer shown in FIG. lb actually surrounds that shown in FIG. 1a.

The Winding mandrel comprises a cylindrical mandrel 1 having a flange 3 in which an inclined slot 5 is provided. The winding wire passes through the slot 5 into the winding mandrel and is led in a manner known per se by means of a winding linger moved, for example, in a stepwise manner so that the position Vof the turns shown in FIG. la is obtained. FIG. la shows that the larger portion of each turn, for example of the lirst turn, is located in a plane at right angles to the axis `of the coil. Only the comparatively small inclined portion which constitutes the transition from a turn to the next one, is not located in the said plane. For the sake of clarity, a

3,088,001 Patented Apr. 30, 1963 coil having only three turns per layer is shown, but this number may naturally be considerably larger.

A second flange 9 `of: the winding mandrel, as may be seen from FIGS. la and 1b, has a particular shape and is arranged to be axially slidable on the mandrel 1. After completion of the lirst winding layer, the ange 9 is moved into the position shown and fixed therein. Due to the presence of the flange 9, the winding wire, in the further process of winding the coil already passes to the second Winding layer before the third turn is completed. The transition portion 11 and the beginning of the second layer are shown in dotted lines in FIG. la. In FIG. 1b such is the case with the transition portion 11.

FIGS. la and lb show that the flange 9 has an axially projecting edge 13 through a large part of its periphery at the level of the second layer, said edge being interrupted through part of its periphery by a recess 1-5. The radial and axial dimensions of the projecting edge 13 are about equal to the diameter of the winding wire 7. The projecting edge 13 supports and guides the winding wire so that the rst (incomplete) turn `16 of the second layer for the greater part lies about in the same plane as the underlying (last) t-urn of the first layer.

As may be seen from FIG. 1b, the first turn 16 of the second layer is located in the recess 15 of the flange edge 13, the angle `et through which the incomplete turn 16 embraces the first layer being determined by the length of the recess 15. The angle a is always less than 360. During the further process of winding the second layer, the turns again settle themselves so that the larger part of each turn is located in a plane at right angles to the axis of the coil. Comparison of FIGS. la and lb shows that each time a turn of the first layer and an upperlying turn of the second layer are located approximately in the same flat plane. FIG. lb shows that the last turn of the second layer (also the last turn of the coil) is likewise incomplete; the missing piece also corresponds to the angle a so that the last turn embraces the underlying turn through the complementary angle 360-a.

The winding wire 7 at the free end of the first turn of the coil located directly under the last turn is now removed from the slot' and bent backwards so that this end runs bilarly with the rst turn. The portion 17 of the winding wire, which bililarly runs backwards, is shown in dotted line in FIG. la. Comparison with FIG. 1b shows that the wire portion 17 bitilarly runs backwards through the angle a (or through a somewhat smaller angle). This may also be seen from FIG. 3 which shows the complete coil from the side which is glued to a diaphragm (see FIG. 2) of a microphone or loudspeaker. The figures show that this side of the coil is as llat as possible so as to obtain optimum adhesion to the diaphragm 19, while the ends 21 and 23 of the winding wire 7 leave the coil about tangentially and in the plane of the first and last turns (see FIG. 3) and thus may readily be glued to the diaphragm.

The angle a is preferably about 180, which implies that the wire portion 17 which bililarly runs backwards (see FIG. 3) extends to a point located approximately diametrically opposite the end 23 of the winding (the relevant wire end 21 is shown in dotted line in FIG. 3). The two ends of the winding may then extend Wholely symmetrically and tangentially with respect to the Winding of the coil, which is very advantageous for obtaining a symmetric structure of the assembly comprising the diaphragm and the driving coil.

The coil shown, which comprises only two layers, is very advantageous :from the viewpoint of a simple and cheap manufacture. However, it is also possible to manufacture a coil having another even number of layers, for example four layers. An example of such a coil is shown in axial section in FIG. 4. For winding this coil, use is preferably made of a stationary winding mandrel and two wire magazines rotating about the winding mandrel in opposite directions. The winding process is started at the center of the inner layer, the rst three layers being wound in the sequence of turns indicated by the meander line in FIG. 4, with the use of the two ordinary smooth anges. The winding wire, which may be covered in known manner with a thin thermoplastic layer, is then xed in position, for example, by heating for a short period, whereafter one ange is replaced by a ange which fundamentally corresponds to the flange 9 of FIG. 1b and which permits the top layer (outer layer) to be wound in the manner previously described.

What is claimed is:

1. An electrodynamic device comprising a diaphragm, a voice coil adhered to said diaphragm, said voice coil having the larger portion of each turn of the coil and any turn positioned above and below located in one and the same plane at right angles to the axis of the coil, the wire ends extend from the outer layer of said coil, the rst and last turn respectively enclose the other layers through an angle a of less than 360 and through at most the complementary angle 360-u respectively, the winding wire at the free end of the first turn of the coil located directly under the last turn runs backwards bilarly with the irst turn in line with the said last turn through `at most the angle a; said winding being so arranged that said voice coil is in relative at engagement with said diaphragm.

2. An electrodynamic device as claimed in claim 1 wherein said angle a is approximately 180.

3. An electrodynamic device as claimed in claim 1 wherein said voice coil comprises two layers.

References Cited in the file of this patent UNITED STATES PATENTS 1,729,806 Thuras Oct. 1, 1929 1,956,826 Engholm May 1, 1934 1,962,012 Grassmann June 5, 1934 2,769,942 Hassan Nov. 6, 1956 2,925,541 Koch Feb. 16, 1960 2,930,014 Van Der Hoek et al Mar. 22, 1960 

1. AN ELECTRODYNAMIC DEVICE COMPRISING A DIAPHRAGM, A VOICE COIL ADHERED TO SAID DIAPHRAGM, SAID VOICE COIL HAVING THE LARGER PORTION OF EACH TURN OF THE COIL AND ANY TURN POSITIONED ABOVE AND BELOW LOCATED IN ONE AND THE SAME PLANE AT RIGHT ANGLES TO THE AXIS OF THE COIL, THE WIRE ENDS EXTEND FROM THE OUTER LAYER OF SAID COIL, THE FIRST AND LAST TURN RESPECTIVELY ENCLOSE THE OTHER LAYERS THROUGH AN ANGLE A OF LESS THAN 360* AND THROUGH AT MOST THE COMPLEMENTARY ANGLE 360* -A RESPECTIVELY, THE WINDING WIRE AT THE FREE END OF THE FIRST TURN OF THE COIL LOCATED DIRECTLY UNDER THE LAST TURN RUNS BACKWARDS BIFILARLY WITH THE FIRST TURN IN LINE WITH THE SAID LAST TURN THROUGH AT MOST THE ANGLE A; SAID WINDING BEING SO ARRANGED THAT SAID VOICE COIL IS IN RELATIVE FLAT ENGAGEMENT WITH SAID DIAPHRAGM. 